In the evolution of automobiles from motorized carriages to highly regulated devices for mass transportation, there has been a continuous pursuit of refinement of the basic combination of elements that comprise the automobile. One aspect of this refinement has been the transmission of torque from the engine to the drive system of the vehicle. This transmission of torque has, throughout, been accomplished by various gear or chain driven transmission systems alternatively drivingly connected to, or disconnected from, a source of motive power. The connection/disconnection feature of the drive system is accomplished by means of a clutch. Since the mid-1950's, especially in the United States, this clutch has been a hydrokinetic torque coupling device or torque converter. Owing to the inclusion of this fluid torque transmitting coupling, enhanced refinement of the driving experience has been obtained, but this refinement came at the expense of lost efficiency. To address this lost efficiency, the torque converter has become, itself, an object of greater refinement and recaptured efficiency. Oftentimes, a modern era torque converter will include a friction clutch assembly associated with a driven member of the torque converter which, at preset loads and speeds, eliminates the fluid transmission of torque and replaces the fluid coupling with a direct mechanical friction coupling. This feature is commonly referred to as a lock-up clutch.
In the era of the lock-up clutch equipped torque converter, efficiency has been recaptured, but a loss of refinement has also occurred when the clutch is in lock-up mode and when it is transitioning into and out of lock-up mode. This is especially true when the lock-up clutch elements become worn and tolerances between various rotating and fixed elements increase/decrease in accord with their respective wear patterns. To alleviate some of the mechanical coarseness created by the incorporation of lock-up clutches onto torque converters, the clutch systems, themselves, have increased in complexity. This added complexity creates the potential for a loss of refinement through vibration caused, in part, by unbalanced decentered rotation of the various components.
Accordingly, the coupling device comprises a torsional vibration damper which is designed to damp the noises and vibrations derived from the engine. This torsional vibration damper comprises first and second damping means which are arranged in parallel by means of a connection disc which is designed to be rendered integral in rotation with one of the drive or driven shafts.
The first damping means comprises resilient units which are distributed circumferentially around the axis of the drive and driven shafts. Each resilient unit extends circumferentially between first support seats which are supported by the connection disc.
The second damping means comprise groups of resilient units, each comprising at least two first resilient units which are arranged in series by means of a first intermediate support element, each group extending circumferentially between second support seats which are supported by the connection disc.
It will be noted that the rigidity of a damper of this type is generally too great to damp vibrations efficiently in the case of transmission of a high level of torque between the engine and the means for changing the gear ratio of the motor vehicle, and in particular torque greater than 400 Nm.
While torsional vibration dampers for the hydrokinetic torque coupling devices, including but not limited to that discussed above, have proven to be acceptable for vehicular driveline applications and conditions, improvements that may enhance their performance and cost are possible.